The present invention relates generally to elevators and, in particular, to an apparatus for detecting and signaling the function and status of a safety disk brake for elevators.
According to the current regulations for elevators, mechanical brakes in elevator drive units have to be constructed as so-called safety or emergency brakes. All of the mechanical parts of such brakes, which parts participate in the braking action onto the brake disk, must exist in duplicate and are designed in such a manner, that in case of failure of one of these parts, a braking action sufficient for the deceleration of the car loaded with a minimal load is maintained on the brake disk.
It is customary for the monitoring of the functions of a safety or emergency disk brake to actuate microswitches attached at appropriate points. The microswitches are actuated by the movements of the brake levers and/or magnetic plungers which, with the respective contact positions, form and influence part of a monitoring and safety circuit. Due to the generally short actuating distances, these microswitches are actuated exclusively by the magnetic plungers or by the end of the longer part of a brake lever. With such an arrangement however, only the simple movements of the two brake levers can be detected. In the case where a brake lever still moves but with reduced force due to the breakage of a spring, this failure is not recognized and a more or less reduced brake action results.
FIG. 1 of the German Patent Specification No. 26 17 882 shows a typical construction of a safety or emergency brake for elevators. It is obvious that appropriate microswitches are attached to the magnet housing and would be actuated by the upper end of the brake lever. The lower part of the magnet housing forms, as is customary, a rigid spring stop center, whereby the breakage of a brake pressure spring would most probably not be noticed immediately. Likewise, an overdue adjustment operation is not indicated.